1. Field of the Invention
The present invention relates to a multifinger hand device having a plurality of finger mechanisms.
2. Description of the Related Art
Multifinger hand devices having a structure similar to the human hand structure include a plurality of finger mechanisms extending from a palm unit. Each of the finger mechanisms comprises a plurality of link mechanisms successively joined by a plurality of joints. The link mechanisms have respective actuators for operating, e.g., bending, the corresponding joints. For details, reference should be made to Japanese laid-open patent publication No. 8-126984, for example.
The conventional multifinger hand devices have been disadvantageous in that the direction of movement and the layout of the joints of each of the finger mechanisms are not necessarily suitable for grasping a variety of different objects or workpieces. Therefore, there has been a demand for an improved multifinger hand device.
It is therefore an object of the present invention to provide a multifinger hand device which is capable of grasping objects or workpieces easily and efficiently.
According to the present invention, a multifinger hand device has a palm unit and a plurality of finger mechanisms extending from said palm unit, each of said finger mechanisms comprising a plurality of link mechanisms successively joined from said panel unit by a plurality of joints. The present invention is basically exemplified in first through third aspects.
According to the first aspect, the finger mechanisms include a finger mechanism corresponding to a thumb (also referred to as xe2x80x9cthumb mechanismxe2x80x9d) and other finger mechanisms. The joints (hereinafter referred to as xe2x80x9cfirst jointxe2x80x9d), which are closest to said palm unit, of said thumb mechanism and at least one (also referred to as xe2x80x9cspecific finger mechanismxe2x80x9d) of said other finger mechanisms are arranged such that a rotational axis about which said joint, closest to said palm unit, of the thumb mechanism is rotatable and a rotational axis about which said joint, closest to said palm unit, of said specific finger mechanism cross each other, preferably cross each other substantially perpendicularly to each other.
With the arrangement of the first aspect, when both or one of the first joint of the thumb mechanism and the first joint of the specific finger mechanism rotates, the portion of the thumb mechanism which is closer to the tip end thereof than the first joint and the portion of the specific finger mechanism which is closer to the tip end thereof than the first joint are brought into facing relation to each other in one plane. Therefore, the multifinger hand device is capable of easily grasping an object between the thumb mechanism and the specific finger mechanism.
In the first aspect of the present invention, each of the other joints than the first joints of the thumb mechanism and the specific finger mechanism may be of such a structure as having a number of degrees of freedom. If each of the other joints has a one degree of freedom, i.e., if it can be rotated about one rotational axis, then the rotational axis should preferably extend perpendicularly to the rotational axis of the first joint.
According to the second aspect, said finger mechanisms include a finger mechanism corresponding to a thumb (thumb mechanism) and other finger mechanisms, the joints of said other finger mechanisms include first joints closest to said palm unit, said first joints being juxtaposed substantially transversely across said palm unit and having respective rotational axes about which the first joints are rotatable and which are oriented substantially perpendicularly to a flat palm surface of said palm unit, and the link mechanisms of said other finger mechanisms include link mechanisms (also referred to as xe2x80x9cfirst link mechanismsxe2x80x9d) coupled to said first joints and closest to said palm unit, said link mechanisms being fixed to said palm unit such that transversely central axes thereof are inclined to each other and extend toward respective tip ends of said other finger mechanisms.
With the arrangement of the second aspect, since the other finger mechanisms, i.e., the finger mechanisms juxtaposed substantially transversely across said palm unit, have the rotational axes of their first joints oriented substantially perpendicularly to the flat palm surface of said palm unit, the portions of these finger mechanisms which are closer to the tip ends than the first joints can be turned substantially along the flat palm surface of said palm unit about the first joints. Because the first link mechanisms of the other finger mechanisms are fixed to the palm unit such that their transversely central axes are inclined to each other and extend toward respective tip ends of said other finger mechanisms, the finger mechanisms can be turned about the rotational axes of the first joints in a wide angular range out of physical interference with adjacent ones of the finger mechanisms. Thus, each of the other finger mechanisms and adjacent ones thereof can be rotated about the rotational axes of the first joints in a relatively wide angular range without being rotated through an unnecessarily large angular interval. As a result, the finger mechanisms can easily be brought into postures suitable for grasping variously shaped objects.
In the second aspect, if each of the joints, other than the first joints, of the other finger mechanisms has a one degree of freedom, then the rotational axis of the joint should preferably extend perpendicularly to the rotational axis of the first joint. If each of the joints of the thumb mechanism has a one degree of freedom, then it is preferable that the rotational axis of the first joint of the thumb mechanism closest to the palm unit extend substantially perpendicularly to the rotational axes of the first joints of the other finger mechanisms and the rotational axes of the other joints of the thumb mechanism extend perpendicularly to the rotational axis of the first joint of the thumb mechanism.
According to the third aspect, the finger mechanisms include a finger mechanism corresponding to a thumb (thumb mechanism) and other finger mechanisms, the joints (first joints), which are closest to said palm unit, of said other finger mechanisms being juxtaposed substantially transversely across said palm unit and having respective rotational axes about which the joints are rotatable, said joints being arranged with their rotational axes inclined to each other in a direction substantially perpendicular to a flat palm surface of said palm unit, and spreading radially toward a back of said palm unit.
With the arrangement of the third aspect, since the rotational axes of the joints, closest to the palm unit, of the other finger mechanisms are inclined to each other in a direction substantially perpendicular to a flat palm surface of said palm unit, and spreading radially toward a back of said palm unit, when the joints of the other finger mechanisms which are closer to the tip ends thereof than the first joints are operated to bend their portions closer to the tip ends thereof than the first joints toward the flat palm surface, the tip ends of the finger mechanisms tend to be brought together. Therefore, the multifinger hand device can easily grasp an object with those finger mechanisms.
In the third aspect, as with the second aspect, if each of the joints, other than the first joints, of the other finger mechanisms has a one degree of freedom, then the rotational axis of the joint should preferably extend perpendicularly to the rotational axis of the first joint. If each of the joints of the thumb mechanism has a one degree of freedom, then it is preferable that the rotational axis of the first joint of the thumb mechanism closest to the palm unit extend substantially perpendicularly to the rotational axes of the first joints of the other finger mechanisms and the rotational axes of the other joints of the thumb mechanism extend perpendicularly to the rotational axis of the first joint of the thumb mechanism.
The first through third aspects of the present invention may be combined with each other. If the second aspect is combined with the first aspect, then the first joints, closest to the palm unit, of the other finger mechanisms have their rotational axes juxtaposed substantially transversely across said palm unit in the direction substantially perpendicular to the flat palm surface of the palm unit, and the link mechanisms of the other finger mechanism, which are connected to the first joints and positioned closest to the palm unit, are fixed to the palm unit such that their transversely central axes are inclined to each other and spread radially toward the tip ends of the finger mechanisms.
If the third aspect is combined with the first aspect, then the joints (first joints), closest to the palm unit, of the other finger mechanisms are juxtaposed substantially transversely across said palm unit, and have their rotational axes inclined to each other in the direction substantially perpendicular to the flat palm surface of the palm unit, and spreading radially toward the back of the palm unit.
If the third aspect is combined with the second aspect, then the first joints of the other finger mechanisms have their rotational axes inclined to each other in the direction substantially perpendicular to the flat palm surface of the palm unit, and spreading radially toward the back of the palm unit.
In either one of the first through third aspects of the present invention, said other finger mechanisms should preferably include at least two finger mechanisms which are structurally identical to each other.
The identical finger mechanisms can be switched around or can replace each other. Therefore, the inventory control for those identical finger mechanisms can be facilitated. When either one of the identical finger mechanisms is broken, it can easily be replaced with a new one of the other finger mechanisms.
In either one of the first through third aspects of the present invention, the multifinger hand device may also have a plurality of actuators mounted respectively in said finger mechanisms for rotating the joints of the finger mechanisms. If at least two of the other finger mechanisms are identical in structure to each other and if they incorporate actuators therein, then the identical finger mechanisms including the actuators can be switched around or can replace each other.
For actuating the joints of the finger mechanisms, each of the link mechanisms other than the link mechanisms closest to the tip ends of the finger mechanisms should preferably be combined with a rotary actuator means such as an electric motor for actuating the joint between itself and an adjacent link mechanism, and a rotation transmitting means, including a speed reducer, for transmitting the rotational power from the rotary actuator means to the joint.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.